On-line electrical equipment often is provided with one or more indicators, visible or audible, of its operational status as active or inactive, on-line or off-line. Recently TVSS apparatus located in a meter adapter, plugging between the conventional watt-hour meter and socket, has been provided with such a visible indicator, as taught in Allina U.S. Pat. No. 4,931,895. That patent discloses a status indicator in the form of a light-emitting diode or equivalent located substantially flush with the outside of the adapter housing.
Off-line status may result either from failure of a normally active component or by action of a protective cutoff device such as a fuse. Allina U.S. Pat. No. 4,866,560 teaches temperature-sensing in TVSS apparatus by such a "thermal" fuse that is not current-limited.
Because most watt-hour meters are located outside a dwelling or other building they are exposed to deleterious sun, rain, wind, etc. A window through which status lights inside can be viewed from outside is taught in Allina U.S. Pat. No. 4,907,119 for TVSS apparatus in a dissimilar housing. There is a continuing need to provide some such status indication without incurring deleterious external exposure.
The aforementioned patents are incorporated in their entirety by this reference for descriptive and illustrative background.
Another problem is that indicator means, however long-lived, may fail earlier if continuously actuated than if only actuated upon demand, as for a status check. The present invention meets both such needs for TVSS apparatus, whether in the form of a so-called meter adapter, which is presented as an example, or in another form.